Four-stroke internal combustion engines which are in use today are subjected to development and improvement continually but their original power transmission form namely the pistons transmitting power to a connecting rod and towards a crankshaft cannot be developed. The movement of the pistons in an engine normally generates friction on a lateral side of the pistons which is the rolling radius side of a crank. The friction causes the pistons and the cylinder to undergo wear and tear and lose energy. Moreover, crankshafts which are in use today have light weight and the friction thus causes energy loss in a useless manner. When a close patent is taken into account such as U.S. Pat. No. 4,106,443 which relates to cylinder heads, there is great development nowadays. However, there are limitations in respect of the size and the number of valves which cause obstacles in the flow of an air-fuel mixture and exhaust gases. Previous development of cylinder heads has dealt with the development of spherical rotary valve assemblies as shown in U.S. Pat. Nos. 4,944,261; 4,989,558. For this new engine type, a cylinder head is constructed to have a rotor blade rotatably fitted in place of a valve. Therefore, the purpose of the present invention is to the construct an assembly with a reduced number of parts and to provide smooth flow of an air-fuel mixture and exhaust gases without the valve face to obstruct the flow of an air-fuel mixture and exhaust gases.